Unlubricated fretting wear of TiB 2 -containing composites against bearing steel
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INTRODUCTION
AT present, there is a tremendous industrial need for new materials or improved existing materials to meet the increasing demand in the tribology world, exemplified by machining and metal forming, bearings, gears, seals, etc.[1] The majority of these applications are currently served by hardened steels and WC-based hardmetals with or without surface coatings. Because of their useful combination of physicomechanical properties (elastic modulus, hardness, and strength) and corrosion resistance, ceramics are recognized as potential materials for tribological applications.[2] Due to its excellent hardness (around 25 GPa), TiB2 is a promising candidate material for tribological applications.[3] In the present study, the dry unlubricated fretting wear of TiB2-containing composites with different binder phases (sialon, Y-TZP, and Ni3(Al,Ti)) is investigated. Steel is selected as a counterbody material, because of its widespread engineering importance. Several studies have examined the wear behavior of advanced structural ceramics. The tribological behavior of TiC-based ceramics against high-speed steel was investigated using a pin-on-disk tribometer.[4] Oxidative wear coupled with adhesive and abrasive wear was the major mechanism for material removal. Rainforth[5] investigated the micromechanical and microchemical processes involved J. VLEUGELS, Professor, K.C. HARI KUMAR and R.G. VITCHEV, Postdoctoral Researchers, and O. VAN DER BIEST, Full Professor, are with the Department of Metallurgy and Materials Engineering, (MTM), Katholieke Universiteit Leuven, B-3001 Leuven (Heverlee), Belgium. Contact e-mail: [email protected] B. BASU, formerly Postdoctoral Student, MTM, Katholieke Universiteit Leuven, is Assistant Professor, Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur, India. Manuscript submitted April 10, 2001. METALLURGICAL AND MATERIALS TRANSACTIONS A
in dry sliding of several zirconia-toughened ceramics (YTZP, Mg-PSZ, and zirconia-toughened aluminum (ZTA)) against bearing steel and ZTA ceramic counterfaces. The wear mechanism in these tribocouples was dominated by the tribochemical reactions at the sliding contacts. The role of zirconia phase transformation was found to be negligible. The influence of a SiC reinforcement on the sliding wear of zirconia against hard metal has been reported.[6] Both tribomechanical and tribochemical wear were found to play significant roles in the wear of the tribocouples. Moreover, the influence of zirconia toughening was found to be important in the abrasive wear resistance of zirconia-toughened MoSi2 and alumina composites sliding against SiC.[7] Although tribological studies on several zirconia-toughened ceramics have been reported in the literature, none of the studies has evaluated the fretting wear performance of zirconia-toughened TiB2 composites. Mukerji et al. studied the wear performance of sialonbased composites with varying amounts of TiC or BN (up to 20 vol pct) against ball bearing–grade steel
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